Investigations of Defect Physics and Quenching Effect for Optimizing n- type Carrier Concentration in CuWO 4 Photocatalyst

As a semiconductor photocatalyst, antiferromagnetic (AFM) CuWO 4 exhibits a weak n -type behavior in experiments, yet the microscopic origins and effective strategies for enhancing its electron concentration ( n 0 ) remain unclear. This study systematically analyzes the self-consistent Fermi level, n 0, and dominant intrinsic defect concentrations in CuWO 4 by using spin-polarized density functional theory and thermodynamic equilibrium simulations. The calculated formation energies indicate that Cu interstitials (Cu i 2+ ), O vacancies ( V O4 2+ ), and Cu vacancies ( V Cu 2– ) are the dominant intrinsic defects in CuWO 4 across relevant chemical potential ranges; however, the low Cu i 2+ and V O4 2+ concentrations and compensation by V Cu 2– result in intrinsically weak n-type conductivity. Moreover, donor ( D + ) and intrinsic defect codoping enhances n 0 only within a narrow optimized chemical potential region ( OCPR ) under Cu-rich/W-rich/O-poor conditions at 300 K, where the compensation between V Cu 2– and D + is suppressed. Remarkably, quenching from 800 to 300 K obviously broadens the OCPR by significantly reducing the V Cu 2– concentration, enabling higher room-temperature n 0 in CuWO 4 with negligible charge compensation and recombination effects. Thus, this study identifies the origins and fundamental bottleneck of weak intrinsic n -type CuWO 4 and provides an experimentally accessible route to obtain higher n -type conductivity in CuWO 4, which could significantly enhance its photocatalytic performance.